Human papillomavirus (HPV) load is higher in HPVDNA/p16 positive than in HPVDNA positive/p16 negative oropharyngeal squamous cell carcinoma but does not differ significantly between various subsites or correlate to survival

Objective: Patients with human papillomavirus DNA positive (HPVDNA⁺) and p16^ink4a overexpressing (p16⁺) oropharyngeal squamous cell carcinoma (OPSCC), especially those with cancer in the tonsillar and base of tongue subsites as compared to other OPSCC subsites have a better outcome than those with only HPVDNA⁺ or only p16⁺ cancer. Likewise having a high viral load has been suggested to be a positive prognostic factor. We therefore hypothesized, that HPV viral load could vary depending on OPSCC subsite, as well as with regard to whether the cancer was HPVDNA⁺ and p16⁺, or only HPVDNA⁺, or only p16⁺ and that this affected outcome.

Material and methods: To address these issues HPV viral load was determined by HPV digital droplet (dd) PCR in tumor biopsies with previously known HPVDNA/p16 status from 270 OPSCC patients diagnosed 2000-2016 in Stockholm, Sweden. More specifically, of these patients 235 had HPVDNA⁺/p16⁺, 10 had HPVDNA⁺/p16^-, 13 had HPVDNA^-/p16⁺ and 12 had HPVDNA^-/p16^- cancer.

Results: We found that HPVDNA⁺/p16⁺ OPSCC had a significantly higher viral load than HPVDNA⁺/p16^- OPSCC. Moreover, there was a tendency for a higher viral load in the tonsillar and base of tongue OPSCC subsites compared to the other subsites and for a low viral load to correlate to a better clinical outcome but none of these tendencies reached statistical significance.

Conclusion: To conclude, the mean viral load in HPVDNA⁺/p16⁺ OPSCC was higher than in HPVDNA⁺/p16^- OPSCC, but there was no statistically significant difference in viral load depending on OPSCC subsite or on clinical outcome.